Which condition can lead to a false high EPR reading while on the ground or in flight?

A false high Engine Pressure Ratio (EPR) reading can occur due to various factors affecting the pressure measurement system. When looking at the potential causes, the presence of ice in the inlet pressure lines is particularly significant.

Ice can obstruct the airflow or create pressure differentials that do not accurately reflect the actual engine operating conditions. When ice forms in the inlet pressure lines, it can cause the measured pressure to be higher than it truly is, resulting in a misleadingly high EPR. This incorrect reading can lead to improper engine management decisions, potentially endangering the aircraft's performance and safety.

On the other hand, low fuel quantity, engine overheating, and leaks in the exhaust system do not typically result in false high EPR readings. Low fuel quantity mainly affects fuel flow and performance but does not interfere directly with the pressure measurement system. Overheating of the engine might lead to other indications of malfunction, but it does not create a false high pressure in the inlet. A leak in the exhaust system tends to produce a drop in pressure readings rather than an artificial increase. Therefore, the condition most likely to result in a false high EPR reading is indeed ice in the inlet pressure lines.